It is common practice in the construction or demolition industry to use hydraulic hammers in order to break up concrete, rock, hard ground, asphalt or unwanted structures for removal or further construction.
A large proportion of the material to be broken up consists of either concrete or asphalt. These materials have very different characteristic and therefore require different type of machinery or tool bits to break them up. Concrete is a very brittle material and can therefore be smashed by impaction. Asphalt is a ductile or ‘plastic’ material that tends to absorb much of the energy applied through impaction. Accordingly, asphalt or similar materials need to be fractured. A finer blade will effectively slice, puncture or crack the material, therefore allowing demolition to be completed by cutting rather than hammering.
Where asphalt is laid over concrete, as with many North American roadways, two types of hammer configurations can be required to complete the job, depending on the thickness of the asphalt. This double layer can therefore mean the need for more than one demolition machine on a job, doubling the cost of demolition and creating down time for the concrete breaker while the asphalt breaker works to expose the concrete.
Furthermore, ground that has been frozen by permafrost, for example in Northern Europe, can also have a very ductile or plastic nature. Consequently, if a blunt ended hammer is used to apply a force, that force may be absorbed by the ground, resulting in either a punched hole and no fracture, or the ground will just rebound due to the elasticity of the peat beneath it. Thus a finer blade tip is required to fracture the material. Again, either further machines are required, or the industry is delayed over the winter months. Furthermore, colder conditions increase the likelihood of damage to the machinery due to temperature gradients forming across the hammer leading to thermal shock and resultant fracture.
The breaking up of ground that is frozen due to permafrost with current technology has proved to be virtually impossible and as such construction is limited to the warmer months that in some cases can be as short as ten to twelve weeks.
It would be an advantage to extend that construction time, even by a few weeks either side of the warmer months.
A typical drop hammer, being one type of demolition hammer device, consists of a heavy plug or column that is raised and then released. Gravity propels the plug or column towards the ground and the type of impact with the ground is determined by the shape of the face of the plug or column that connects with the ground.
It would be an advantage to be able to easily vary the nature of the impact beneath the drop hammer so as to enable a single machine to operate in various conditions with different types of materials. However, any ability to vary the nature of the impact must be combined with the usual durability and overall strength required by the industry. It would be a limitation to produce a system that could be varied, but required high maintenance or a large period of downtime to implement.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.